list_calendar_namesLists the calendars in the Mac's Calendar app (Calendar.app, local/iCloud). For Microsoft 365 calendars use the m365 calendar tools instead.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
| Name | Required | Description | Default |
|---|---|---|---|
| count | No | ||
| calendars | No |
Changes observed during successful MCP inspections.
Output schema / properties / calendars / items / properties / sourceAdded value: +{
+ "description": "Owning account (iCloud, Exchange, an email address, On My Mac). Two calendars can share a title across accounts — use this (or id) to disambiguate.",
+ "type": "string"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and destructiveHint=false, so the read-only nature is clear. The description adds useful context about the specific app (Calendar.app) and scope (local/iCloud), which goes beyond the annotations. No additional behavioral details like return format or edge cases are needed for such a simple list operation.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two sentences, zero fluff. The first sentence states the function; the second provides the alternative. Every word earns its place, and the most important information is front-loaded.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a zero-parameter, read-only list tool with an output schema and sibling tools, the description is complete. It specifies the source (Mac Calendar app), the scope (local/iCloud), and differentiates from M365 tools. No additional context is needed.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The tool has 0 parameters, and the schema is empty (100% coverage). Baseline is 4, and the description correctly avoids inventing parameter details that don't exist. It would be inappropriate to add parameter semantics where none are needed.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the tool lists calendars in the Mac's Calendar app (Calendar.app, local/iCloud). It uses a specific verb and resource, and explicitly distinguishes itself from Microsoft 365 calendar tools by directing users to the m365 alternatives.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
It explicitly states when to use this tool (for local/iCloud calendars) and when not to (for Microsoft 365 calendars, use m365 calendar tools). This provides clear guidance and names the alternative toolset.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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